Comparative corrosion study of Ag-Pd and Co-Cr alloys used in dental applications

Abstract

The electrochemical behaviour of two Ag-Pd alloys (Unique White and Paliag) used in dental prosthetics construction for crowns and bridges and one Co-Cr alloy (Vitallium 2000) was studied in artificial saliva using the polarization curves and electrochemical impedance spectroscopy (EIS). The corrosion resistance was evaluated by means of the corrosion currents value and by coulometric analysis. The open circuit potential of Ag-Pd are attributed to dealloying followed by surface enrichment with Ag and the possible formation of an insoluble AgCl surface film on the respective alloy surfaces. Our results have shown that these alloys have a somewhat good corrosion resistance in artificial saliva. The corrosion current densities of Unique White and Vitallium 2000 alloys were very low (~100 nA/cm 2 ). For Ag-Pd alloys, when increasing the content of Cu, corrosion resistance decreases. The passivation of all samples occurred spontaneously at the open circuit potential. The electrochemical properties of the spontaneously passivated electrodes at the open circuit potential were studied by EIS. The polarization resistance (R p ) and the electrode capacitance (C dl ) were determined. The polarization resistance of all the samples increases with the immersion time. The polarization resistances are largest for Unique White (Ag-Pd) and Vitallium 2000 (Co-Cr) alloys. Because the electrochemical behaviour of the Co-Cr alloy was compared with that of Ag-Pd alloy, this type of alloy may be a suitable alternative for use in the manufacture of fixed dental prostheses. The present study, though limited, has shown that electrochemical characteristics can be used to identify such alloys. Knowledge of the in vitro corrosion behaviour of these alloys may lead to better understanding of any biologically adverse effects in vitro.

Investigation of the Microstructure, Hardness and Corrosion Resistance of a New 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn Dental Alloy

“…The two Tafel lines intercept at the point of the coordinates (Ecor, Icor). As was reported [19], an alloy with a tendency toward passivation will have a value of b a > b c , while an alloy that corrodes will have a b a < b c . The Icor is the most representative for the degradation degree of the alloy as it measures the net ion flux density through the double electric layer around the working electrode.…”

“…The traces of the Vickers indentations on three representative areas of a polished specimen of 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn are shown in Figure 10. The average microhardness of the specimen is 206 µHV40 which is significantly higher than that of the Paliag whose value is 180 µHV40 [19].…”

“…Recent trends have shown that low-noble dental alloys (Ag and Pd alloys, known as white alloys) are attracting much attention as alternatives to Au alloys because of their lower price [6][7][8]. Thus, Ag-based alloys such as Ag-Pd-Cu-Au [9][10][11][12][13][14][15][16][17][18][19], and Ag-Cu-Pd-Au [20,21] alloys have reached commercial status. Alloys like Unique White 66Ag 22Pd 10Cu 1In (wt%) and Paliag 50Ag 30Pd 15 9Cu 3Au 1Zn have achieved large recognition on the dental alloy market [22].…”

Influence of orientation on corrosion behavior of directionally solidified cobalt‐base superalloy

“…In addition to elevated temperature oxidation behavior , the general corrosion behavior of such alloy on different orientations is equally worthwhile to investigate for practical applications. The corrosion behaviors of pure cobalt and some conventional cobalt alloys were well studied in the literature. Pure cobalt shows good passivity in neutral and alkaline solutions.…”

“…Besides, the addition of special element will enhance corrosion resistance. For example, a sufficient amount of chromium to pure cobalt reduces the corrosion rate considerably in acidic, neutral and alkaline solutions , and the addition of W is conducive to a stable passive layer in alkaline and acidic solutions, while no such protecting layers were obtained in neutral solutions . Moreover, the corrosion behavior of novel γ/γ’‐strengthened cobalt‐base alloy including oxidation property and electrochemical performance was investigated .…”